Seabed Drilling
A seabed rig which could be used to drill for gas hydrates is being developed, as Giovanni Spagnoli and Leonhard Weixler (executive director) from the Department of Maritime Technologies at BAUER Maschinen explain
Sea floor drilling D
rilling for natural resources offshore, such as oil and gas, or for soil sam-
pling, in some instances hun- dreds of miles away from the nearest landmass, poses a num- ber of different challenges over drilling onshore.
The actual drilling mecha- nism used to drill into the sea floor is much the same as can be found on an onshore rig. However, with drilling at sea, the sea floor can sometimes be thousands of metres below sea level. Dedicated drill ships are used in science and in the industry in order to get long cores both from soft sediments and hard rocks. However, these special ves-
sels are expensive and their op- eration is not time effective when only short drilling is re- quired.
The drill string has to be built up through the entire water column before sampling
can be started. Precise naviga- tion and heave compensation are required in order to min- imise disturbances during the coring process and to control drill-bit pressure.
Especially in the upper tens to one hundred metres, core quality is usually poor when drilling with a drill ship into the deep sea floor.
Subsea drilling equipment began to appear in commercial use in the 1970s. The earliest examples of these units were diver operated, marinised ter- restrial single-shot rotary dia- mond core drilling rigs used for shallow rock coring for survey purposes. They also found application installing the small diameter piles which are used to restrain and stabilise oil and gas pipelines in shallow water zones with rocky seabeds, such as those found in the Persian Gulf and NW Australia coastal oil fields.
The sea floor drill rig could be used instead of a drillship in certain circumstances
Giovanni Spagnoli, product manager for maritime technologies at BAUER Maschinen
More recent developments focus on multi barrel sea bed drill rigs for deeper penetration. Marum has developed and
operates the sea floor drill rig MeBo (Meeresboden-Bohrgerät - German for “sea floor drill rig”).
This drill rig is capable of sampling soft sediments and hard rocks down to 80m from the sea floor. It can be operated in water depths up to 2,000m. The MeBo can be deployed
from standard research vessels such as the RV Meteor and RV Sonne.
The development of the
drill was funded by the German Ministry of Education and Re- search and by the Bremen State Government.
The MeBo is a portable drill rig which is remotely operated from the vessel. A steel armoured umbilical
manufactured by the Nord- deutsche Seekabelwerke (NSW) is used to lower the MeBo to the sea bed. Copper wires and fibre op- tics in the umbilical core are used for energy supply and for
12 November/December 2012 Offshore Technology
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